public FunctionExpression ParseFunctionExpression()
{
var funcDec = new FunctionExpression { Token = Next() };
Match(TokenType.Func);
if (Next().Is(TokenType.Identifier))
{
funcDec.Identifier = ParseIdentifier();
}
funcDec.FormalParameters = ParseFormalParameterList();
funcDec.Body = ParseFunctionBody();
return funcDec;
}